1. Field of the Invention
The present invention relates to an optical lens device assembly comprising two optical lens devices and more particularly to an ideal optical lens device assembly being made up of microlenses.
2. Description of the Related Art
In optical communications, in order to guide signal light from, for example, a laser diode used as a light emitting element into an optical fiber, a combination of microlenses each having a diameter of a hundred and several tens xcexc m is employed.
As shown, for example, in xe2x80x9cProceeding SPIExe2x80x9d (Vol. 3631, p234-243) issued in April 1999 which has disclosed such the microlens, a plurality of microlenses each having a columnar shape is collectively by bundling many cylindrical optical elements each having an outer diameter being equal to that of an optical fiber to be optically coupled to the microlens and performing photolithography and etching processing, by one operation, on end faces of the optical elements to collectively form specified lens planes on each of end faces of many optical elements.
Also, by forming many lens planes on an optical substrate made up of, for example, a silicon crystal at regular intervals and then coating lens portions containing each lens plane with a etching mask and by performing etching processing on the substrate region being exposed from the above mask to form many columnar microlenses portions each having a lens plane at each end on an optical substrate and then by separating each of the microlenses portions from the optical substrate, many columnar microlenses can be also formed collectively.
Such the microlens is used in a form of a lens device assembly constructed by combining a first microlens adapted to convert diverging light emitted from a light emitting element to a collimated beam with a second microlens adapted to gather the collimated beam transferred through the microlens at an end of an optical fiber. To guide the diverging light emitted from the light emitting element into the optical fiber, the lens device assembly made up of the first and second microlenses is placed between the light emitting element and the optical fiber.
The optical fiber is placed in a V-shaped groove formed, by photolithography and etching technologies, which are generally used in Si LSI manufacturing processs, relative to the light emitting element with high accuracy, on a substrate, thus enabling highly accurate alignment of an optical axis of the light emitting element and that of the optical fiber. Moreover, as described above, by serially placing two columnar microlenes each having an outer diameter being approximately equal to that of the optical fiber in the V-shaped groove, it is made possible to fitly place the two microlenses by a passive alignment method using no monitoring light and without the occurrence of a deviation in the optical axis.
However, the conventional microlens has a problem. That is, the conventional microlens made up of a columnar optical element with a lens plane on its one end generally has a shape of a truncated cone because a diameter of the optical element is easily changed along its optical axis due to errors in manufacturing the microlens. When two microlenses having the truncated cone shape are serially placed in the groove, a great deviation occurs in the optical axis depending on a form of placement of these two microlenses.
In view of the above, the present invention has an object that is to provide an optical lens device assembly which can decrease a deviation between optical axes of two optical lenses caused by manufacturing errors, thus can prevent a drop in coupling efficiency.
According to a first aspect of the present invention, there is provided an optical lens device assembly including:
two optical lens devices each having a truncated cone shape as a whole and being made up of an optical element one end face of which serves as a lens plane and another end face of which serves as a non-lens plane, and being placed on a reference plane so as to be optically coupled in series; and
wherein the two optical lens devices are placed in a manner that the non-lens planes of the two optical lens devices face each other.
In this optical lens device assembly, the two optical lens devices may be placed in a manner that either smaller end faces of the two optical lens devices face each other or larger end faces of the two optical lens devices face each other.
Also, the two optical lens devices may be placed so as to be symmetric with respect to a virtual intermediate plane between the two optical lens devices.
Also, a smaller end face of one optical lens device may face a larger end face of another optical lens device.
Also, the two optical lens devices may be placed in a manner that smaller end faces of the two optical lens devices are aligned in same direction and larger end faces of the two optical lens devices are aligned in same direction.
According to a second aspect of the present invention, there is provided an optical lens device assembly including:
two optical lens devices each having a truncated cone shape as a whole and being made up of an optical element one end face of which serves as a lens plane and another end face of which serves as a non-lens plane, and being placed on a reference plane so as to be optically coupled in series; and
wherein the two optical lens devices are placed in a manner that planes of outgoing light of the two optical lens devices serve as the lens plane.
In this optical lens device assembly, the two optical lens devices may be placed in a manner that either smaller end faces of the two optical lens devices face each other or larger end faces of the two optical lens devices face each other.
Also, the two optical lens devices may be placed so as to be symmetric with respect to a virtual intermediate plane between the two optical lens devices.
Also, a smaller end face of one optical lens device may face a larger end face of another optical lens device.
Also, the two optical lens devices may be placed in a manner that smaller end faces of the two optical lens devices are aligned in same direction and larger end faces of the two optical lens devices are aligned in same direction.
Moreover, in the foregoing, the two optical lens devices may be placed in a concave groove formed on a substrate providing the reference plane in which optical fiber being optically coupled to the optical lens device is placed.
Also, the two optical lens devices may be microlenses.
Also, the two optical lens devices may be microlens made of a silicon crystal substrate.
With the above configurations, by placing both the microlenses according to the specified placements described above respectively, the optical axes of the two optical microlenses can be adjusted easily. Therefore, even if each of the microlenses is changed to a truncated cone shape due to the manufacturing errors so that it can not show a cylindrical shape as a whole, the deviation between the optical axes can be decreased. As a result, it is possible to prevent easily a drop in the substantial coupling efficiency.